Debt and Credit Agreements - Narrative (Details) $ / shares in Units, shares in Millions					1 Months Ended	12 Months Ended
		Feb. 29, 2016 USD ($)	Dec. 02, 2015 USD ($)	Sep. 30, 2013 MW	Jun. 30, 2014 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2016 USD ($)	May 26, 2016 USD ($)		Apr. 01, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jan. 13, 2016 USD ($)	Jan. 05, 2016 USD ($)	Oct. 23, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jul. 30, 2015	Jun. 30, 2015 USD ($) $ / shares	Sep. 30, 2014 USD ($)	Sep. 18, 2014 USD ($)	May 31, 2014 USD ($)	Feb. 06, 2014 USD ($)	Aug. 10, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 30, 2012 USD ($)	Oct. 31, 2011 USD ($)	Aug. 01, 2011 USD ($)	Jul. 31, 2011 USD ($)
Debt Instrument [Line Items]
Long-term Debt, Current Maturities						$ 2,430,000,000	$ 1,500,000,000
Repayments of Long-term Debt						1,936,000,000	2,687,000,000	$ 1,545,000,000
Escrow Deposit						6,000,000
Gain (Loss) on Sale of Debt Investments						$ 37,000,000
Credit agreement threshold						2.50
Outstanding letters of credit	[1]					$ 1,510,000,000
Basis points adders for prime-based borrowings						27.50%
Basis points adders for LIBOR-based borrowings						127.5
Bridge loan									$ 3,200,000,000.0													$ 7,200,000,000.0
Long-term debt, gross						$ 33,311,000,000	25,113,000,000
Long-term debt						33,959,000,000
Redemption of debt						45,000,000	44,000,000
Collateral amount of debt						2,800,000,000
Line of Credit Facility, Increase (Decrease), Other, Net		$ 45,000,000
Secured Demand Note Deficiency		$ 23,000,000
Outstanding borrowings/facility draws						75,000,000
Debt Instrument, Fee Amount			$ 5,000,000
Payments of Debt Issuance Costs			4,000,000
Write off of Deferred Debt Issuance Cost			9,000,000
Redemption Premium			9,000,000
Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Notional amount of preissuance interest rate cash flow hedge derivatives						659,000,000
Upstream Gas Property [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						15,000,000
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross						11,868,000,000	9,803,000,000
Debt Instrument, Face Amount									$ 4,200,000,000
Redemption of debt			868,000,000
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term debt, gross						$ 1,150,000,000	1,150,000,000												$ 1,150,000,000.00
Equity units issued | shares					23
Conversion price | $ / shares																			$ 50
Proceeds from issuance of subordinated long-term debt					$ 1,110,000,000
Underwriting fee					$ 35,000,000
Long-term debt																			$ 131,000,000
Maximum [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings						9000.00%
Basis points adders for LIBOR-based borrowings						165.0
Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						7.60%
Maximum [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						6.50%
Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						1.55%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					$ 9,500,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity										$ 600,000,000	[2]													$ 500,000,000
Line of Credit Facility, Maximum Amount Outstanding During Period						$ 250,000,000
Credit agreement threshold						500
Exelon Corporate [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 46,000,000	2,263,000,000	23,000,000
Outstanding letters of credit	[1]					29,000,000
Long-term debt, gross						7,608,000,000	5,853,000,000
Long-term debt						7,608,000,000
Debt Instrument, Face Amount			$ 1,900,000,000
Outstanding borrowings/facility draws						0
Exelon Corporate [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term debt, gross						$ 1,150,000,000	1,150,000,000
Interest rate on long-term debt						6.50%
Exelon Corporate [Member] | Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt	[3]					7.60%
Exelon Corporate [Member] | Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt	[3]					1.60%
Exelon Corporate [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[4],[5]					$ 600,000,000
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities						1,117,000,000	90,000,000
Repayments of Long-term Debt						$ 202,000,000	89,000,000	586,000,000
Credit agreement threshold						3.00
Outstanding letters of credit						$ 1,170,000,000
Basis points adders for prime-based borrowings						27.50%
Basis points adders for LIBOR-based borrowings						127.5
Long-term debt, gross						$ 9,208,000,000	8,919,000,000
Long-term debt						9,208,000,000
Outstanding borrowings/facility draws						$ 0
Line of Credit Facility, Description						100
Exelon Generation Co L L C [Member] | ExGen Texas Power [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt																					2.34%
Non-recourse debt, interest rate swap																					$ 505,000,000
Exelon Generation Co L L C [Member] | ExgenRenewablesI425June62021[Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt																							2.03%
Non-recourse debt, interest rate swap																							$ 240,000,000
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross						$ 5,971,000,000	5,971,000,000
Debt Instrument, Face Amount						750,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt																					4.75%
Debt Instrument, Face Amount																					$ 675,000,000
Non-recourse debt						660,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | ExgenRenewablesI425June62021[Member]
Debt Instrument [Line Items]
Interest rate on long-term debt																							4.25%
Long-term debt																							$ 300,000,000
Non-recourse debt						234,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | DOE Project Financing, 3.092% January 2, 2037 [Member]
Debt Instrument [Line Items]
Outstanding letters of credit						106,000,000
Non-recourse debt, commitment																									$ 646,000,000
Non-recourse debt						552,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Denver International Airport [Member]
Debt Instrument [Line Items]
Outstanding borrowings/facility draws																										$ 7,000,000
Non-recourse debt						6,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Holyoke [Member]
Debt Instrument [Line Items]
Outstanding borrowings/facility draws																											$ 11,000,000
Non-recourse debt						9,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Upstream Gas Property [Member]
Debt Instrument [Line Items]
Non-recourse debt, commitment																													$ 85,000,000
Non-recourse debt, commitment increase available																													$ 500,000,000
Outstanding borrowings/facility draws						22,000,000
Non-recourse debt						68,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | SolGen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount																					$ 150,000,000
Non-recourse debt						148,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Renewable Power Generation [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount													$ 150,000,000
Non-recourse debt						141,000,000
Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Continetal Wind [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity																	$ 131,000,000
Outstanding letters of credit						108,000,000
Interest rate on long-term debt																				6.00%
Debt Instrument, Face Amount																				$ 613,000,000
Generation capacity of portfolio | MW				667
Aggregate bank commitments under unsecured revolving credit facilities																				$ 10,000,000
Non-recourse debt						$ 543,000,000
Exelon Generation Co L L C [Member] | Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						7.60%
Exelon Generation Co L L C [Member] | Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						2.00%
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 5,300,000,000
Exelon Generation Co L L C [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					500,000,000
Outstanding letters of credit	[1]					306,000,000
Outstanding borrowings/facility draws						75,000,000
Exelon Generation Co L L C [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity												$ 200,000,000			$ 150,000,000	$ 100,000,000
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Outstanding letters of credit						500,000,000	275,000,000
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities						425,000,000	665,000,000
Repayments of Long-term Debt						$ 665,000,000	260,000,000	617,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 2,000,000
Basis points adders for prime-based borrowings						7.50%
Basis points adders for LIBOR-based borrowings						107.5
Long-term debt, gross						$ 7,101,000,000	6,567,000,000
Long-term debt						7,307,000,000
Outstanding borrowings/facility draws						0
Commonwealth Edison Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2],[4],[5]					1,000,000,000
PECO Energy Co [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 300,000,000	0	250,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 2,000,000
Basis points adders for prime-based borrowings						0.00%
Basis points adders for LIBOR-based borrowings						90.0
Long-term debt, gross						$ 2,600,000,000	2,600,000,000
Long-term debt						2,784,000,000
Outstanding borrowings/facility draws						0
PECO Energy Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2],[4],[5]					600,000,000
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 379,000,000	75,000,000	70,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 0
Basis points adders for prime-based borrowings						0.00%
Basis points adders for LIBOR-based borrowings						100.0
Long-term debt, gross						$ 2,341,000,000	1,870,000,000
Long-term debt						2,599,000,000
Outstanding borrowings/facility draws						0
Baltimore Gas and Electric Company [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross						$ 2,300,000,000	1,750,000,000
Baltimore Gas and Electric Company [Member] | Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						6.35%
Baltimore Gas and Electric Company [Member] | Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on long-term debt						2.40%
Baltimore Gas and Electric Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					$ 600,000,000
Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term debt, gross						5,157,000,000	5,331,000,000
Long-term debt						5,157,000,000
Repayments of Bank Debt						300,000,000
Short-term Bank Loans and Notes Payable														$ 500,000,000
Short-term Debt, Percentage Bearing Variable Interest Rate														1.00%				950000.00%
Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity										$ 900,000,000																		$ 1,500,000,000
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases																												$ 500,000,000
Line of Credit Facility, Maximum Amount Outstanding During Period						$ 750,000,000
Credit agreement threshold						1.25
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 11,000,000	22,000,000	184,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 0
Basis points adders for prime-based borrowings						7.50%
Basis points adders for LIBOR-based borrowings						107.5
Long-term debt, gross						$ 2,381,000,000	2,385,000,000
Long-term debt						2,381,000,000
Outstanding borrowings/facility draws						0
Potomac Electric Power Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					300,000,000
Delmarva Power and Light Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities						105,000,000
Repayments of Long-term Debt						$ 100,000,000	100,000,000	100,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 0
Basis points adders for prime-based borrowings						7.50%
Basis points adders for LIBOR-based borrowings						107.5
Long-term debt, gross						$ 1,348,000,000	1,273,000,000
Long-term debt						1,348,000,000
Outstanding borrowings/facility draws						0
Delmarva Power and Light Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					300,000,000
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 48,000,000	58,000,000	$ 66,000,000
Credit agreement threshold						2.00
Outstanding letters of credit	[1]					$ 1,000,000
Basis points adders for prime-based borrowings						7.50%
Basis points adders for LIBOR-based borrowings						107.5
Long-term debt, gross						$ 1,162,000,000	$ 1,210,000,000
Long-term debt						1,162,000,000
Outstanding borrowings/facility draws						0
Atlantic City Electric Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	[2]					$ 300,000,000

[1] Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.

[2] Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

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[4] Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015, respectively

[5] Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million, $5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.